1. Field of the Invention
The present invention relates to a pressure-reduced chamber system for loading/unloading an object to/from a process chamber, and more specifically to a load lock chamber including a loading/unloading mechanism for loading/unloading a semiconductor wafer to/from the process chamber of a magnetron plasma etching device.
2. Description of the Related Art
A process chamber, for example, for etching a semiconductor wafer under a reduced pressure, has a load lock chamber at each of the entrance and exit thereof, through which the wafer is loaded and/or unloaded. The load lock chamber is communicated to an exhausting device so that the pressure in the load lock chamber is reduced to the same level as the inner pressure of the process chamber in a short period of time. Further, a handling device for loading/unloading the semiconductor wafer to/from the process chamber is housed in the load lock chamber.
Load lock chambers having such a handling device are disclosed in Published Unexamined Japanese Patent Applications Nos. 54-10976, 62-16167, 61-278149, 62-150735, 62-21644, 60-120520, 60-183736, 62-21649, 62-161608, 61-99345, 61-99344, 61-90903, 61-90887, 61-87351, 61-71383 and 62-41129. The handling devices set forth in these documents include expansible multi-joint arms and a driving mechanism therefor.
The driving mechanisms of these handling devices include a number of mechanisms such as a gear, belt, pulley, and the like, and as these mechanisms slide with each other with some inevitable friction, fine particles are generated therefrom. If these fine particles generated from the mechanisms are scattered in the load lock chamber, some of them are accumulated on the surface of a wafer, and/or even come into the process chamber, thereby disturbing the process of the wafer in the process chamber. In order to avoid such a problem, the mechanisms for driving arms are usually housed in dust protective casings.
However, in the conventional devices, when the inner pressure of the load lock chamber is being reduced from that of the atmosphere to that set for the process, the dusts generated from the driving mechanisms leak out from the casing. In this case, it is not possible to completely remove the leaking dust from the load lock chamber; therefore some of the dust flow into the process chamber from the load lock chamber, and accumulate on the wafer, rendering the wafer a defective product.